So I bought the 8700 bb off ebay and when I got it everything worked fine, except when I received a call I could hear the other person, but the person cannot hear me. I dont know what to do to fix this. Anytime I make a call or receive one, I can hear the other person, but they cannot hear me.

I am not sure on the microphone, it may be a bad part. You might want to contact the seller and see if you can work something out. The only thing I can think to try is a battery pull.

As far as the contacts you can wipe the device. It will remove all data so if there is something in there that you have addes it will be gone. To restore to the factory defaults. Menu>options>Security Options>General Settings>Menu>Wipe Handhelp.